Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor. The rotor typically includes a rotatable hub having one or more rotor blades attached thereto. A pitch bearing is typically configured operably between the hub and the rotor blade to allow for rotation about a pitch axis. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Changes in atmospheric conditions, for example, wind speed, wind turbulence, wind gusts, wind direction, and density may significantly influence power produced by the generator. A power output of the generator increases with wind speed until the wind speed reaches a rated wind speed for the turbine. At and above the rated wind speed, the generator operates at a rated power. The rated power is an output power at which the generator can operate with a level of fatigue or extreme load to turbine components that is predetermined to be acceptable. At wind speeds higher than a certain speed, typically referred to as a trip limit, the wind turbine may implement a control action, such as shutting down or de-rating the wind turbine in order to protect wind turbine components from damage. In addition, there may be certain wind speeds and/or operational set points (such as generator speed or power) that lead to a corrective action (such as a pitch control action) below rated power.
In certain control systems, such as the system described in U.S. Pat. No. 9,605,558 filed on Aug. 20, 2013 entitled “System and Method for Preventing Excessive Loading on a Wind Turbine” which is incorporated herein by reference in its entirety, a wind condition is estimated using wind turbine operating data, a series of equations, and one or more aerodynamic performance maps. The aerodynamic performance map(s) are dimensional or non-dimensional tables or graphs that describe rotor loading and performance (e.g. power, thrust, torque, bending moment, or similar) under given conditions (e.g. density, wind speed, rotor speed, pitch angles, or similar). As such, the aerodynamic performance map(s) may include: power coefficient, thrust coefficient, torque coefficient, and/or partial derivatives with respect to pitch angle, rotor speed, or tip speed ratio. Alternatively, the aerodynamic performance maps can be dimensional power, thrust, and/or torque values instead of coefficients. Once the desired coefficients are known, the controller can control the wind turbine based thereon.
The aerodynamic performance map(s) mentioned above are static and are typically determined during a design stage of the wind turbine. Therefore, the aerodynamic performance map(s) are not dependent upon changing wind conditions that may be present during operation of the wind turbine, such as wind speed, turbulence intensity, wind shear, or sudden wind gusts.
Accordingly, a system and method for controlling a wind turbine that included adjustment factors for the aerodynamic performance maps to account for wind shear, turbulence intensity, and/or blade aerodynamic shape would be desired in the art.